At present, a capsule filling machine normally comprises a central turret or carousel that rotates intermittently and that is equipped with a plurality of operating units positioned around the periphery of the turret and driven by the turret itself through intermittent drive means.
Each operating unit around the turret comprises a mounting slide holding one or more capsules to be transported to a plurality of working stations which perform, according to a known method, the various steps in the process cycle, that is to say, feeding and orienting the closed capsules, opening each capsule by separating the capsule body from the capsule lid, filling a quantity of pharmaceutical material into the capsule body, closing the capsule body with its lid and, lastly, expelling the full closed capsule thus made.
Following a predetermined cycle, dosing units of known type, each comprising a hollow cylindrical punch with a piston inside it (usually pneumatically driven), withdraw the pharmaceutical material by lowering the cylindrical punch into the pharmaceutical material contained in a tank associated with the turret and then lifting the piston in such a way as to draw a predetermined dose of the material into the cylindrical punch previously lowered into the tank.
Next, the cylindrical punch is lifted out of the tank and after removing excess material from it by scraping or brushing, the piston is lowered in such a way as to push the volumetric dose of material out of the cylindrical punch chamber and into the capsule body that has in the meantime lined up with it.
At present, dosing units of this type are used to good advantage to precisely dose pharmaceutical material in powder form, whereas, if the capsules have to be filled with particulate material such as microtablets or micropellets, dosing is not equally precise.
Indeed, whereas the piston in the cylindrical punch can withdraw constantly precise, volumetrically dosed quantities of pharmaceutical material in powder form, in the case of microtablets, pellets or the like, the force applied by the piston is not equally effective in withdrawing predetermined, constant numbers of microtablets to be filled into the respective capsule bodies.